stoekle



Patented July '15, 1919.

2 SHEETSSHEET l- F IL K E 0 T S R r.

THERMIONIC AMPLIFIER.

. APPLICATION FILED JUNE 13. I917. 1,809,704.

E. R. STOEKLE.

THERMIONIC AMPLIFIER.

APPLICATION FILED JUNE 13.1911.

1,309,704. Patented July 15, 1919.

2 SHEE-TSSHEET 2.

55615 Wham.

UNITED STATES PATENT oFFIoE.

ERWIN B. STOEKLE, OF NEW YORK N. Y'., ASSIGNOB TO THE CUTLER-HAMMER MFG.

(10., OF MILWAUKEE, WISCONSIN,

A CORPORATION OF WISCONSIN.

THEBMIONIC AMPLIFIER.

Specification of Letters Patent. Patented July 15, 1919.

Application filed June 13, 1917. Serial No. 174,417.

comprise a vacuum tube containing an anode, a grld and an incandescent cathode capable of emitting electrons. The incandescent cathode usually consists of a filament heated by an electric current. In such a cathode there is a potential difference of the heating current at different points along a the filament and this results in distorting the electrical field between the cathode and the id and anode. The amount of this distortion depends upon the magnitude of the potential difference of the heating current as compared to the, potentials of the anode and grid. In tubes designed for large thermionic currents it is necessary to have a large area of hot cathode. The current necessary to heat this large cathode area cannot be supplied at high potential without causing a very great distortion of the fields between the cathode and the other electrodes. Therefore it has been necessary to introduce large currents at low potential to heat the cathode but this is objectionable in that it requires the use of large platinum seals to, conduct the current into the tube. It has been found in practice that it is very desirable. to have the incandescent cathode at a single, potential at all points on its surface so that the electrical fields between the cathode and. grid and anode will not be distorted. 'Previous attempts to produce an equipotential cathode have not been wholly satisfactory as they have the disadvantage among other things of requiring the use of relatively high voltages.

One object of this invention is to provide an improved amplifier having a cathode which operates at a single potential throughout its surface or area.

Another object is to provide an improved method of heating the cathode.

. ings in which Another object is to provide an improved amplifier in which there will be no distortion of the fields between the cathode grid and anode.

Another object is to heat the cathode by an independent gas or'vapo'r discharge.

Another object is to provide an amplifier which is more efiicient than amplifiers heretofore used.

Other objects will appear as the specification proceeds.

The invention is somewhat diagrammatically illustrated in the acct mpanylng draw.-

Figure 1 is a front elevation of a thermionic amplifier constructed in accordance with the invention.

Fig. 2 is a front elevation of an amplifier differing from the amplifier shown in Fig. 1

only in structure and not in operation.

Fig. 3 is a front elevation of an amplifier having different 'means for heating the amplifier cathode. 1

Fig. 4 is a front elevation of an amplifier differing from the amplifier shown in Fig.

3 only in structure and not in operation.

Fig. 5 isafront elevation of an amplifier having still different means for heating the amplifier cathode, and

Figs. 6,' 7 and 8 are schematic diagrams showing how the amplifiers of Figs. 1, 3 and 5 may be connected with gthjer devices in the system.

The improved amplifier comprises in general a vacuum tube containing an anode, a grid and a cathode. The anode and grid may be of usual construction but the cathode is of novel construction andis heated in a novel manner. The cathode divides the tube into two separate compartments. The pure electron discharge takes place in the u per compartment from the upper surface 0 the cathode. The lower sur ace of the cathode is subjected to a vapor or gaseous discharge which takes place in the lower compartment from an auxiliary cathode located in this compartment. The amplifier cathode to be heated, forms the anode of this auxiliary discharge. The-bombardment of the back of the amplifier cathode by'the negative ions of the auxilia discharge serves to heat the cathode. The eating current for the amplifier cathode is therefore at right angles to ,fall of potential along the surface.

Figs. 1 to 5 inclusive show different forms of amplifiers constructed in accordance with the invention, and Figs. 6 to 8 inclusive show how some of these amplifiers may be connected in circuit with the other devices inthe system.

In Fig. 1 the vacuum tube is shown at 1. It may be of any convenient shape. The tube is divided into two compartments 2 and 3 which. are separated by the amplifier cathode 4. The cathode 4 is disk shaped and is hermetically sealed in the tube. It isconnected to wires 5 and 5 which lead to the outside of the tube. The compartments of the tube are highly evacuated and for this purpose small outlet tubes 6 and 7 may be provided.

The grid is shown at 8. It may be of usual construction and has a mesh determined by the amplification desired. The grid is supported in proper relation with the cathode 4 by arms 9 and 10. A wire 11 is electrically connected to the grid and leads to a point outside of the tube.

The anode for receiving the electrons emitted from the amplifier cathode is shownat 12 and may also be of the usual construction. It .is supported by the arms 9 and 10 and is electrically connected with a wire 13 that extends to a point outside of the tube.

In the compartment 3 there is located a mercury cathode 14 and an auxiliary starting electrode 15. Current is'conductcd to these electrodes by means of the conductors 16 and 17 respectively. A mercury arc may be maintained between the mercury cathode 14 and the lower surface of the amplifier cathode 4. The lower surface of the electrode 4 then becomes an anode for the auxiliary discharge in the compartment 3 and the upper surface of the electrode 4 serves as the cathode or electron emitting surface for the pure electron discharge in compartment 2. The electrode 4 will be raised to a temperature by the mercury arc which depends upon the energy supplied to the are. If desired the upper surface of the electrode 4 may be coated with alkaline earth oxide to increase its ability to emit the electrons. The walls of the tube below the cathode 4, may be depressed if desired as shown at 45 to form a restricted throat for the purpose of localizing the stream of ionized vapor on the central part of the amplifier cathode. This avoids excessive heating of that portion of the cathode in contact with the walls of the tube.

It will now be seen that the upper surface of electrode 4 which serves as the cathode for the amplifier is an equipotential surface with respect to the grid 8 and the anode 12 and therefore the electrical partment 3 and the outer surface is the cathode or the electron emitting surface for the pure electron discharge in compartment 2. The grid 8 and anode 12 are also made cylindrical in shape and are supported in proper relation with the electrode 4 by means of the arms 9 and 10'. Conductors 5, 5, 11 and 13 are connected to the electrodes as in Fig. 1, and lead to points outside of the tube. The operation of this type of amplifier-is the same as that shown in Fig. 1.

In Fig. 3 the anode 12, grid 8, and amplifier cathode 4 are constructed and arranged in the same manner as in Fig. 1, but the auxiliary heating discharge is produced in a different manner. Instead of using a mercury are as in Fig. 1 a gaseous discharge is employed. For this purpose a filament 18 is located in the compartment and current is supplied to the filament by conductors 19 and 20. The compartment 3 is filled with nitrogen, argon or other inert gas at reduced pressure. The filament when heated maintains the ionization of the nert gas in compartment 3. The filament is used as a cathode for the auxiliary discharge while the amplifier cathode 4 serves as the anode for the auxiliary discharge and is heated thereby. The material of which the cathode 4 is made, and the inert gas for the compartment 2, should be so chosen that the gas will notpenetrate the hot cathode and destroy the vacuum in the compartment 2.

In Fig. 4 an amplifier is illustrated which operates on the same principles as the aimplifier just described, but the electrodes are made cylindrical in shape as in Fig. 2. The filament 18' extends into the interior of the cylindrical amplifier cathode 4'. I

Fig. 5 shows an amplifier like that shown in Fig. 3, but the hot filament is replaced by an electrode 21 connected to asingle conductor 22. The are between the electrode L1 and the amplifier cathode 4 is started by employing a,relatively high initial voltage which may be reduced after the discharge begins. ()ne way of accomplishing this will be later explained when the external connections of this type of amplifier are described.

The improved amplifier may be used in any system where it is desirable to use a device of this character. The external connections will depend largely upon the type.

ternal connections for the type of amplifier shown inFi 5.

In Fig.6t e roper terminals of a battery 23 are connected to the anode 12 and cathode 4 byconductors 24, 25 and 26. The battery is in series with terminals 27 and 28 to which is connected the circuit in'which it is desired to amplify the energy" variations. The rid 8 is connected to the negative termina of a battery 29 by a conductor 30. The positive terminal of the battery 29 is connected to a terminal 31. The'cathode 4 is connected by a conductor 32 to a terminal 33. The terminals 31 and '33 are connected to thecircuit carrying the small energy variations which are to be amplified. The battery 34 maintains the mercu'r arc between the mercury cathode 14 ah the amplifier cathode 4, a variable resistance 35 in serie with the are being provided to control the intensity of the arc and therefore the temperature of the cathode. -A switch 36 is provided to temporarily supplycurrent to the auxiliary starting'electrode 15.

In Fig. 7 the connections for the amplifier proper are the same as in Fig. 6, but the connections for the auxiliary heating discharge are somewhat different. In thisfigure the filament 18 is connected across part of the battery 34 by conductors 37, 38 and 39. The other part of the battery 34 maintains the amplifier cathode 4 at a positive potential with respect to filament 18, so as to set up a stream of ionized gas between the filament and amplifier cathode for the purpose of heating the latter. Variable resistances 40 are provided to vary the temperature of the amplifier cathode 4 by varying theintensity of the stream of Ionized gas, passing between the filament 18 and the cathode 4. k

In Fig. 8 the connections for the am lifier proper are the same as in Figs. 6 and but the connections for the auxiliary heating discharge are as follows:'

The battery 34 is connected to the ampli-- fier cathode 4 and the electrode 21 in the same manner as it is connected to the-corresponding electrodes in Fi 6, the variable resist ance 35 being provi ed to vary the tempera: ture of the amplifier cathode 4by varyin the intensity of t e stream of ionized gas rom the electrode 21. In order to start the dishharge in this type of amplifier it is necesthe value required for normal operation. In

order to supply this starting potential a switch 41 and inductance 42 are shunted around the battery 34 by conductors 43 and 44. When the switch 41 is closed it connects the inductance 42 across the battery 34 and when the switch 41 is opened the self induced elcctromotive force sufiiciently raises the potential between electrode 21 and amplifier cathode 4 to start the arc. After the arc is established the potential of the battery 34 is sufficient to maintain the are.

It will now be seen that in all of the forms of the amplifier above described the amplifier cathode is heated in such a manner that it operates at .a single potential throughout its area because the heating current is substantially at right angles to the cathode surface. There will therefore be no distortion of the fields between the amplifier electrodes even when a relatively high heating current is employed. This result is obtained by the use of an auxiliary vapor or gaseous discharge in a separate compartment of the amplifier. The auxiliary discharge is therefore entirely independent of the pure electron discharge of the amplifier and does not require the use of relative high voltages. The amplifier is therefore more efficient than any heretofore devised.

The various electrodes may be made of any desired shape, the flat and cylindrical types of electrodes being herein illustrated merely to show that the exact shape of .the electrodes is immaterial to the invention. Furthermore, other means,fwithin the'scope of the invention, may be devised for heating the cathode to produce the results herein described and therefore I do not wish to limit myself to the exact means or method disclosed.

Although the improved method of and means for heating the cathode have been described in connection with the cathode of a thermionic amplifier, it may be found useful in other relations and therefore I do not wish to limit myself to its use in connection with amplifiers.

' What I claim is:

1. The method of heating the cathode of a thermionic amplifier or the like, which consists in generating an auxiliary gas or vapor discharge which is independent of the main discharge and of which said cathode serves as the anode.

2. The method of heating the cathode of a thermionic amplifier or thelike, which "consists in subjecting said cathode to a gas or vapor discharge which is inde endent of the main discharge of the ampli er.

3. The method of heating the cathode of a thermionic amplifier or the like, which consists in subjecting said cathode to a gas or vapor discharge, which is separate and distinct from the main discharge of the amplifier. a

4. The combination with the cathode of an electrical discharge device, of means for heating said cathode comprising means for generating a gas or vapor discharge which is independent of the main discharge and of which said cathode serves as the anode.

5. An electrical discharge device comprising a tube having two separate non-communicating compartments, a plurality of electrodes in one compartment comprisingan electron emitting cathode, and means in the other compartment for generating a gas or vapor discharge which serves to heat said cathode. v

6; An electrical discharge device comprising a tube having two separate non-communicating compartments, a plurality of electrodes in one compartment comprising an electron emitting cathode, and means in the interior of said first compartment and another surface exposed to the interior of the second compartment, and means located in said second compartment for producing a gas or vapor discharge to heat said cathode.

In witness whereof, I have hereunto subscribed my name.

ERWIN R. STOEKLE. 

